Paleontology is the study of the history of life on Earth. Paleontologists look at fossils, which are the ancient remains of plants, animals, and other living things. Fossils are mainly formed in two ways. In one case, animal or plant matter is replaced by rock over time, but the remains keep their original shape. In the other case, the fossil is an impression that has been made in rock. It can be a footprint, for example, or the outline of a body pressed into mud.

Paleontologists use fossil remains to understand how species evolve. The theory of evolution says that living species change over a long period of time. Paleontologists study species that still exist and also species that have gone extinct, or died out.

Fossils can give information about an animal or plant's life and environment. For example, oyster shells have one ring for every year of life. An oyster fossil can help paleontologists discover how long that oyster lived. It can also show what the environment was like around the oyster. If the climate was good, the oyster would have grown more quickly and its rings would be thicker. If the oyster struggled to survive, the rings would be thinner. Thin rings mean the environment was not healthy for oysters and similar creatures. Maybe the water was too warm or too cold for them.

Some kinds of fossils provide information about many different sorts of living things. Amber is one example. Amber is fossilized tree sap. When sticky sap dripped down a tree trunk, it has sometimes trapped small insects, and even things like frogs and lizards. Paleontologists study amber to observe these complete specimens. Amber can preserve things as delicate as dragonfly wings.

Fossils can also help show how living beings evolved over time. For example, paleontologists believe whales evolved from land animals. They reached this conclusion based on the fossils of extinct animals that are closely related to whales. These animals lived in the ocean, but still had something similar to legs.

Subdisciplines of Paleontology

The field of paleontology has many subdisciplines. A subdiscipline is a smaller field of study within a larger subject.

Vertebrate Paleontology

One subdiscipline of paleontology is vertebrate paleontology. It is the study of fossils of animals with backbones. Vertebrate paleontologists have discovered the skeletons of dinosaurs and many other ancient animals. They have been able to show how these animals lived and evolved.

Take the example of pterosaurs, a group of flying reptiles. One type of pterosaur, Quetzalcoatlus, was one of the largest flying creatures in history. It had an 11-meter (36-foot) wingspan. That's about as long as a telephone pole.

From looking at fossils, vertebrate paleontologists figured out that pterosaurs had hollow and light bones like birds do today. This made them realize the animals could fly by flapping their wings, rather than just by gliding. Otherwise, the bones would have been too heavy for the pterosaurs to lift off.

Invertebrate Paleontology

Invertebrate paleontologists study the fossils of animals without backbones. Mollusks, corals, crabs, shrimp, sponges and worms are all examples of invertebrates. Unlike vertebrates, invertebrates do not have bones. However, they do leave behind traces of themselves. This evidence includes fossilized shells and impressions of soft body parts. It can even include tracks along the ground or ocean floor.

Invertebrate fossils are especially important to the study of past environments. For example, large groups of 200-million-year-old invertebrate marine fossils have been found in the deserts of Nevada. They tell us that parts of the state were once covered by water.

Paleobotany

Paleobotanists study the fossils of ancient plants. These fossils can be impressions of plants left on rock surfaces. Or, they can be parts of the plants themselves that have been preserved in rock. These fossils reveal how plants have evolved. They also help scientists understand what ancient environments were like.

Micropaleontology

Micropaleontology is the study of fossils of tiny, microscopic organisms. Micropaleontologists use powerful microscopes to study fossils smaller than four millimeters (0.16 inches).

Micropaleontologists often study fossils to better understand how Earth's climate has changed. For example, they study the shells of deep-sea microorganisms. Such creatures make their shells out of elements found in the ocean water around them. These shells tell us what the ocean was like when the creatures were alive. If we know what the ocean was like, we can guess what the climate was like. By studying shells from different periods, micropaleontologists can learn how the climate changed over time.

History of Paleontology

People around the world have been uncovering fossils for thousands of years. They did not always understand what these objects were, though.

Paleontology, as we know it today, began in the 1700s. At that point, scientists carefully studied and classified fossils for the first time. In the 1850s, scientist Charles Darwin suggested that new species evolve over time. Over millions of years, a species can change and become a new species, Darwin said. Creatures today are related to different species from the distant past.

After learning about Darwin's theory of evolution, paleontologists began drawing connections between ancient fossils and living creatures. For example, paleontologists discovered that the prehistoric Archaeopteryx had wings like a bird. At the same time, it had the kind of teeth found in a type of dinosaur called theropods. Paleontologists concluded that the Archaeopteryx was a very early kind of bird. This was one of the first steps in the path from ancient dinosaurs to modern birds.

In the late 1800s, scientists discovered radioactivity. Radioactive objects send out a certain amount of energy over time. By measuring how much radioactive material a fossil has, scientists can guess the fossil's age. This is called radiometric dating.

Paleontology Today

Now paleontologists use many advanced tools. Electron microscopes allow them to study the tiniest details of the smallest fossils. X-ray machines and CT scanners show the inside of fossils. Advanced computer programs can show whole skeletons. They can even show how extinct animals looked and moved.

Paleontologists still make discoveries with simple tools, too. Around the world, scientists are still digging away with pickaxes. Every paleontologist is hoping to shed new light on the evolution of life.